Carbon brushes and connector means



Feb. 14, 1967 R. e. HURRELL ETAL 3,304,452

CARBON BRUSHES AND CONNECTOR MEANS Filed July 2, 1964 United States Patent Ofiice 3,304,452 CARBON BRUSHES AND CONNECTOR MEANS Richard George Hurrell and John Leslie Ayres, London,

England, assignors to Morganite Carbon Limited, London, England Filed July 2, 1964, Ser. No. 379,844 Claims priority, application Great Britain, Apr. 2, 1964, 13,620/64 Claims. (Cl. 310249) This invention relates to carbon brushes, for use in electrical apparatus such as generators, and its object is to provide a carbon brush to which a. flexible connector, usually of braided or twisted copper wire, is firmly and securely attached.

Carbon brushes are known in which the flexible connector is secured to the brush by passing an end portion of the flexible connector through a hole through the brush, splaying the protruding end of the flexible connector, and then soldering the splayed end to a coating of copper or other suitable metal locally applied by electrolysis or by means of a spray gun to the external surface of the brush.

Such carbon brushes have the drawback that, while a pull along the flexible connector can be resisted so that no breakdown of the connection between the brush and the flexible connector occurs, a thrust along the length of the flexible connector towards the brush tends to cause rupture of the bond between the carbon and the surface layer of copper or other metal to which the splayed end of the connector is solder-ed. If such rupture occurs, the brush becomes loose on the connector and good electrical connection between the connector and the brush is lost.

The present invention enables the connector of a carbon brush to be secured so that both pull and thrust along the length of the connector can be resisted without breakdown of the electrical and mechanical connection between the connector and the carbon brush.

Accordingly, the invention provides an electrical contact brush consisting of a block of carbon with a flexible electrical connector, made of metal strands, secured thereto by one end of the connector inserted in a transverse hole through one end of the brush and, according to the invention, a metal sleeve on the end of the connector in the hole in the block has a flange in abutment with the block at one end of the hole therein, to prevent the sleeve from being thrust from the hole in one axial direction, and metal strands of the connector at the extremity thereof at the other end of the hole are splayed radially outwardly beyond the sleeve and soldered to the sleeve to form a head in abutment with the block to prevent the connector from being withdrawn from the hole in the other axial direction.

In such a carbon brush, the splayed soldered head on the end of the flexible connector and the flange of the sleeve act as abutments through which forces acting along the length of the connector are transmitted directly to the carbon of the brush without reliance, as in previous brushes, solely on a bond between the carbon and a surface layer of metal applied thereto.

Accordingly, substantial forces acting in either direction along the length of the connector can be withstood without breakdown in the mechanical connection b tween the carbon brush and its connector.

Electrical connect-ion between the flexible connector and the carbon of the brush can be improved by soldering the splayed end of the connect-or not only to the sleeve but also to a coating of metal, for example copper, previously applied to the surface of the carbon at the adjacent end of the hole.

Preferably, the coating of metal extends over the internal wall surface of the hole in which the sleeve lies 3,304,452 Patented Feb. 14, 1967 so that the sleeve can be soldered thereto to assist in obtaining good electrical connection between the flexible connector and the brush while at the same time adding to the mechanical strength of the connection.

In order to facilitate the entry of solder between the wall of the hole and the sleeve, the transverse dimensions of the sleeve are preferably somewhat smaller than the corresponding dimensions of the hole.

The invention will now be more fully described with reference, by way of example, to the accompanying drawings, in which:

FIG. 1 is a part-sectional, side elevation of a carbon brush having a flexible connector secured thereto, and

FIG. 2 is an axial section of a flanged sleeve.

As shown in FIG. 1, a flexible connector 1 of braided copper wire is secured to a carbon brush 2, consisting of a rectangular block of carbon, by a flanged sleeve 3 which is a tight fit on an end portion 4 of the flexible connector 1 thrust axially into a circular hole 5 at one end of the block.

The hole 5 extends transversely between the faces 6 and 7 of the block and has a counter-bore 8, 9 at each end.

The flanged sleeve 3, shown in sect-ion in FIG. 2, is of -a suitable metal such as tinned copper and is thrust into the hole to bring its flange 11 into abutment with the bottom of the counter-bore 8.

The extremity of the end portion 4 of the connector projects beyond that end of the sleeve remote from the flange 11 and into the counter-bore 9, where it is splayed, so that, when solder is applied thereto, the solder, with the splayed strands of the conector, fills the counter-bore 9 and forms a head 10 on the connector which abuts against the bottom of the counter-bore 9 and prevents the connector from being withdrawn from the hole.

At the same time, solder runs down between the strands of the connector and into the sleeve to solder the connector and sleeve together and assist in preventing the connector being pushed further through the sleeve.

To ensure good electrical connection between the connector and the carbon of the brush, the outer diameter of the sleeve is chosen to be somewhat less than the internal diameter of the hole and, prior to the insertion of the sleeve and connector into the hole, the side wall of the hole and at least the surface of the counter-bore 9 have a coating of suitable metal such as copper, applied thereto by spraying or by electrolysis. Thus, during soldering, solder can pass between the sleeve and the metal coating on the wall of the hole, to make a good electrical and mechanical connections between the sleeve and the surrounding carbon, and between the head 10 and the surface of the counter-bore 9.

We claim:

1. In an electrical contact brush comprising a block of carbon, an arrangement for connecting to the brush a flexible electrical connector composed of metal strands, said arrangement including:

a transverse bore completely through the said brush,

said connector passing completely through said bore from a first bore end to a second bore end, one end of said connector being slightly beyond said second bore end,

a metal sleeve mounted in said bore around the connector, said sleeve having a flange at one end thereof in abutment with said block around the said first bore end thereby preventing the sleeve from being thrust towards the second end of the bore,

the other end of said sleeve remote end terminating at a bore end,

the metal strands at the said other end of the connector being splayed radially outwardly from the from said flange point proximate to the second bore passing radially of the over over the said other sleeve end,

and a metal solder connection between the said splayed end and the said other end of the sleeve,

the said metal solder connection being in the form of a head which includes the metal solder and the splayed ends of the flexible connection and which extends radially outwardly from the sides of the bore and is in abutment with said block around the said second bore end thereby .preventing the sleeve and solder connection from being thrust towards the first end of the bore.

2. An arrangement according to claim 1, in which said hole has a counterbore at each of said sides of said block and said flange of said sleeve and said head respectively are located repectively in said counterbores.

3. An arrangement as claimed in claim 1 including a solder connection between the portions of the sleeve be- 4 tween the head and flange and the said transverse bore.

4. An arrangement according to claim 1, including a coating of metal on at least one of the internal wall surfaces of said hole and on the adjacent surface of said 0pp-osite side of said block.

5. An arrangement as claimed in claim 4 including a solder connection securing the said sleeve to the metal coating, 7 1

References Cited by the Examiner UNITED STATES .PATENTS i v 764,391 7/1904 Street 310 249 1,122,495 12/1914 Gindre 310-449 1,441,640 1/1923 Taylor 310 249 MILTON O. HIRSHFIELD, Primary Examiner.

D. F. DUGGAN, Assistant Examiner. 

1. IN AN ELECTRICAL CONTACT BRUSH COMPRISING A BLOCK OF CARBON, AN ARRANGEMENT FOR CONNECTING TO THE BRUSH A FLEXIBLE ELECTRICAL CONNECTOR COMPOSED OF METAL STRANDS, SAID ARRANGEMENT INCLUDING: A TRANSVERSE BORE COMPLETELY THROUGH THE SAID BRUSH, SAID CONNECTOR PASSING COMPLETELY THROUGH SAID BORE FROM A FIRST BORE END TO A SECOND BORE END, ONE END OF SAID CONNECTOR BEING SLIGHTLY BEYOND SAID SECOND BORE END, A METAL SLEEVE MOUNTED IN SAID BORE AROUND THE CONNECTOR, SAID SLEEVE HAVING A FLANGE AT ONE END THEREOF IN ABUTMENT WITH SAID BLOCK AROUND THE SAID FIRST BORE END THEREBY PREVENTING THE SLEEVE FROM BEING THRUST TOWARDS THE SECOND END OF THE BORE, THE OTHER END OF SAID SLEEVE REMOTE FROM SAID FLANGE END TERMINATING AT A POINT PROXIMATE TO THE SECOND BORE END, THE METAL STRANDS AT THE SAID OTHER END OF THE CONNECTOR BEING SPLAYED RADIALLY OUTWARDLY FROM THE BORE PASSING RADIALLY OF THE OVER OVER THE SAID OTHER SLEEVE END, AND A METAL SOLDER CONNECTION BETWEEN THE SAID SPLAYED END AND THE SAID OTHE END OF THE SLEEVE, THE SAID METAL SOLDER CONNECTION BEING IN THE FORM OF A HEAD WHICH INCLUDES THE METAL SOLDER AND THE SPLAYED ENDS OF THE FLEXIBLE CONNECTION AND WHICH EXTENDS RADIALLY OUTWARDLY FROM THE SIDES OF THE BORE AND IS IN ABUTMENT WITH SAID BLOCK AROUND THE SAID SECOND BORE END THEREBY PREVENTING THE SLEEVE AND SOLDER CONNECTION FROM BEING THRUST TOWARDS THE FIRST END OF THE BORE. 